/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package samples.websocket.tomcat.snake;

import java.io.IOException;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Deque;

import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;

public class Snake
{
    
    private static final int DEFAULT_LENGTH = 5;
    
    private final Deque<Location> tail = new ArrayDeque<>();
    
    private final Object monitor = new Object();
    
    private final int id;
    
    private final WebSocketSession session;
    
    private final String hexColor;
    
    private Direction direction;
    
    private int length = DEFAULT_LENGTH;
    
    private Location head;
    
    public Snake(int id, WebSocketSession session)
    {
        this.id = id;
        this.session = session;
        this.hexColor = SnakeUtils.getRandomHexColor();
        resetState();
    }
    
    private void resetState()
    {
        this.direction = Direction.NONE;
        this.head = SnakeUtils.getRandomLocation();
        this.tail.clear();
        this.length = DEFAULT_LENGTH;
    }
    
    private void kill()
        throws IOException
    {
        synchronized (this.monitor)
        {
            resetState();
            sendMessage("{'type': 'dead'}");
        }
    }
    
    private void reward()
        throws IOException
    {
        synchronized (this.monitor)
        {
            this.length++;
            sendMessage("{'type': 'kill'}");
        }
    }
    
    protected void sendMessage(String msg)
        throws IOException
    {
        this.session.sendMessage(new TextMessage(msg));
    }
    
    public void update(Collection<Snake> snakes)
        throws Exception
    {
        synchronized (this.monitor)
        {
            Location nextLocation = this.head.getAdjacentLocation(this.direction);
            if (nextLocation.x >= SnakeUtils.PLAYFIELD_WIDTH)
            {
                nextLocation.x = 0;
            }
            if (nextLocation.y >= SnakeUtils.PLAYFIELD_HEIGHT)
            {
                nextLocation.y = 0;
            }
            if (nextLocation.x < 0)
            {
                nextLocation.x = SnakeUtils.PLAYFIELD_WIDTH;
            }
            if (nextLocation.y < 0)
            {
                nextLocation.y = SnakeUtils.PLAYFIELD_HEIGHT;
            }
            if (this.direction != Direction.NONE)
            {
                this.tail.addFirst(this.head);
                if (this.tail.size() > this.length)
                {
                    this.tail.removeLast();
                }
                this.head = nextLocation;
            }
            
            handleCollisions(snakes);
        }
    }
    
    private void handleCollisions(Collection<Snake> snakes)
        throws Exception
    {
        for (Snake snake : snakes)
        {
            boolean headCollision = this.id != snake.id && snake.getHead().equals(this.head);
            boolean tailCollision = snake.getTail().contains(this.head);
            if (headCollision || tailCollision)
            {
                kill();
                if (this.id != snake.id)
                {
                    snake.reward();
                }
            }
        }
    }
    
    public Location getHead()
    {
        synchronized (this.monitor)
        {
            return this.head;
        }
    }
    
    public Collection<Location> getTail()
    {
        synchronized (this.monitor)
        {
            return this.tail;
        }
    }
    
    public void setDirection(Direction direction)
    {
        synchronized (this.monitor)
        {
            this.direction = direction;
        }
    }
    
    public String getLocationsJson()
    {
        synchronized (this.monitor)
        {
            StringBuilder sb = new StringBuilder();
            sb.append(String.format("{x: %d, y: %d}", Integer.valueOf(this.head.x), Integer.valueOf(this.head.y)));
            for (Location location : this.tail)
            {
                sb.append(',');
                sb.append(String.format("{x: %d, y: %d}", Integer.valueOf(location.x), Integer.valueOf(location.y)));
            }
            return String.format("{'id':%d,'body':[%s]}", Integer.valueOf(this.id), sb.toString());
        }
    }
    
    public int getId()
    {
        return this.id;
    }
    
    public String getHexColor()
    {
        return this.hexColor;
    }
    
}
